Fabrication of semiconductor devices includes interconnect structures to provide electrical connection between active components in the semiconductor devices. The interconnect structure is formed by creating openings for vias and lines in a dielectric material. Metal layers are then deposited in the openings to form a conductive path to provide electrical connection between the active components.
Physical vapor deposition (PVD) or sputtering is an effective means of depositing metal layers to interconnect structures. Sputtering is performed by introducing a gas into a sputtering chamber and igniting the gas to form a plasma. The plasma is then directed at a target comprising a metal material to be deposited on a wafer or substrate. The plasma physically removes atoms or atomic groups from the target. The atoms are attracted to a wafer or substrate by a bias applied to a support on which the wafer is positioned. The atoms contact the wafer and form metal layers on exposed surfaces of the wafer.
A magnet module located at a side of the target away from the wafer is used to disperse the plasma over a surface of the target. The magnet module includes several magnets which form magnetic fields which attract the plasma increasing the density of the plasma near the surface of the target. A rate of sputtering is directly related to the plasma density. In conventional techniques, the magnet module is rotated about an axis which is centered in the chamber. The rotation of the magnet module changes the location of the magnetic fields and therefore the location of the higher plasma density.